This invention relates to voltage regulators and, more particularly, to a voltage regulator for regulating the supply of power by a controlled field generator used to charge an electrical storage device such as a storage battery.
A voltage regulator is commonly used in an electrical system of a vehicle having a controlled field generator for charging the vehicle battery and for supplying power to system loads. The controlled field generator can be either a D.C. generator or an A.C. generator. The voltage regulator controls or regulates the charging of the battery by the generator in response to the battery voltage. When the battery voltage exceeds a predetermined level, which is the design or operating voltage of the battery, the voltage regulator inhibits the generator from further charging the battery, whereas when the battery voltage falls below this predetermined level, the voltage regulator enables further charging of the battery by the generator to increase the battery voltage.
To accomplish this control, the voltage regulator has a circuit that turns on and off the field current to the controlled field winding of the generator. When the battery is fully charged to the operating voltage, the field current is turned off, whereas when the battery voltage is below the operating level the field current is turned on to charge the battery via the output of the generator. Prior voltage regulators disadvantageously use a linear or analog control circuit to turn the field current on and off. As a result of this linear operation, highly precise control is difficult to obtain and the control circuit is relatively complex. Such a linear control circuit also does not have the highest reliability and is expensive.
Furthermore, excessive load current can damage the generator. It is therefore desirable to protect the generator when such excessive load current occurs.